That's a bit faster than the 2.5 percent pace of the second quarter. According to the BEA, consumer spending, inventory investment and exports helped fuel slightly stronger growth.

As we wrote earlier, economists had been expecting to hear that gross domestic product growth slowed from July 1 through Sept. 30, to a 2 percent annual rate. Their prediction may still turn out to be correct: The GDP data will be revised twice; one time each in the next two months.

Our original post — Coming Up: First Look At How Economy Fared In Third Quarter:

We'll likely hear this hour that the U.S. economy slowed in the third quarter, with gross domestic product growth at a 2 percent annual rate versus the previous quarter's 2.5 percent, forecasters tell Reuters.

News of slower growth before the shutdown would also support the view of many experts that "it's difficult to see the economy taking off in the near term," Standard Chartered Bank economist Thomas Costerg says in Reuters' report.

This morning's report will be the first of three in coming months about the third quarter. As happened with the second-quarter data, initial estimates are often revised. The bureau initially said growth in the second quarter registered at just a 1.7 percent annual rate. As more data came in, it raised the estimate to that 2.5 percent annual rate.

Also due at 8:30 a.m. ET: The latest data on weekly claims for jobless benefits.